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BlendLuxCore IES Omnidirectional Point Source Doesn't Match Luxcore Point Source in Intensity

Posted: Sun Mar 28, 2021 12:27 pm
by Jan
I created an IES file with Easy IES. It's a 360 degrees omnidirectional and emitting equal intensities from all directions
Snap1.jpg

For the Blender setup two point white light sources with 80 candela intensities (Luxcore IES Lights and Luxcore Point Source light) and each is situated at the center of two similar 100% matte hemisphere objects with radii of 1 meter. For rendering Total Path Depth is set to 1 to disable all indirect bounce lights inside the hemisphere.
Snap3.jpg

After analyzing the results I found that the illuminances and luminances on both illuminated hemisphere objects are different. Checking the color values in the linear EXR file indicated that their luminances differ by a factor of around 12.6 and the Luxcore IES Lights illuminated hemisphere object dimmer than Luxcore point light illuminated hemisphere object.
Snap4.jpg

Why do they differ despite both are set at the same intensities??? I also don't think the Lumen values in the IES file has any effect on the intensities as well.

Re: BlendLuxCore IES Omnidirectional Point Source Doesn't Match Luxcore Point Source in Intensity

Posted: Sun Mar 28, 2021 8:13 pm
by lighting_freak
Hi,

Interesting finding. Also the factor of 12.6 between the values is very close to 4*pi (full sphere solid angle). Is this coincidence?

Looking forward to the solution.

BR

Re: BlendLuxCore IES Omnidirectional Point Source Doesn't Match Luxcore Point Source in Intensity

Posted: Mon Mar 29, 2021 4:47 am
by Jan
lighting_freak wrote: Sun Mar 28, 2021 8:13 pm Hi,

Interesting finding. Also the factor of 12.6 between the values is very close to 4*pi (full sphere solid angle). Is this coincidence?

Looking forward to the solution.

BR
Hi,

For me it's exactly 4*Pi if without noise.

Rendered with Irradiance Contour Lines 21 steps around 2 min 3 sec time:
12.6x80cd.jpg
12.6 x 80 candela = 1,008

12.56637x80cd.jpg
12.56637 x 80 candela = 1,005.31

Thanks